A typical liquid crystal display device includes a timing controller and a power management module. The timing controller generates a clock signal through a digital supply voltage provided by the power management module. However, when a typical power management module is at a soft start stage and because a surge protection function is not yet activated, an overshoot voltage appears in an output terminal. FIG. 1 shows a waveform of an output voltage from the typical power management module, where the x-axis designates the time axis and the y-axis designates the voltage value. From time 0 to t1, a growth rate of the output voltage (i.e., slope) is k1. When the time is at t1, the voltage value is m, such as 3.3V. However, after the time t1, the output voltage continues to increase, and then is decreased to m again. That is, from time t1 to t2, the voltage value is greater than 3.3V, so that the overshoot voltage appears. Moreover, at this stage, the growth rate of the voltage is obviously greater than k1. If the overshoot voltage appears in the output voltage from the power management module, it is easy to damage the timing controller, thereby increasing manufacturing cost.
Accordingly, it is necessary to provide a digital power supply circuit and a liquid crystal driving device to solve the technical problem in the prior art.